Such a cutting insert is known, for example, from U.S. Pat. No. 6,447,219 which discloses a cutting insert comprising a rear shank portion and a forward cutting head projecting forwardly from the rear shank portion. The cutting head includes a top side, an underside, two flank side surfaces each interconnecting the top side with the underside, and a forwardly facing front flank surface interconnecting the flank side surfaces. Each flank side surface forms an acute angle with the top side. A transition between the flank front surface and the top side forms a main cutting edge. A transition between each flank side surface and the top side forms a side cutting edge. The side cutting edges extend on respective opposite sides of a center line of the cutting head and converge in a forward direction. The side cutting edges form an acute angle between one another. Each side cutting edge includes a plurality of spaced-apart grooves formed therein, whereby each side cutting edge is non-continuous. Therefore, the cutting edge comprises cutting edge segments, each segment separated from an adjacent one by a groove.
During a grooving operation, first the main cutting edge engages the workpiece. As the cutting depth increases, the interaction between the insert and the workpiece occurs on three different sides, i.e. along the major cutting edge and the two side cutting edges at which point the grooves begin to play an active role and contribute to reducing the width of the chips. This helps to avoid the formation of chips which are too thin and difficult to handle. However, consecutive cutting edge segments do not overlap in a direction perpendicular to the direction of feed (i.e., perpendicular to the center line). Consequently, as the cutting depth increases, after a given cutting edge segment has completed machining the workpiece, a portion of the workpiece will engage the groove that is located immediately to the rear (i.e., downstream relative to the feed direction) of the given cutting edge segment. This will result in large forces of resistance being applied to the cutting insert, each time a further groove engages the workpiece. The grooves are not cutting edges and therefore as the cutting depth increases those parts of the workpiece engaging the grooves will not be cut, but at the best deformed. The whole machining process will therefore be very inefficient.